ScienceAsia 27 (2001) : 035-040 |doi: 10.2306/scienceasia1513-1874.2001.27.035

Fiber Optic Sensing Applications Based on Optical Propagation Mode Time Delay Measurement

PP Yupapina^a,* and S Piengbangyang^b

ABSTRACT: This paper presents the study of the feasibility of using a linearly polarized, highly coherent source, ie HeNe laser with wavelength of 632.8 nm, to produce the optical mode delay time in an optical fiber for the use of sensing applications. Results obtained have shown that the propagation mode delay time measurement in term of optical path difference of 50 m was achieved respect to the external applied force of 5 N, on the sensing fiber. Other sensing applications such as displacement and bending sensors were also investigated, where the change in optical path difference in term of output detected mode shift of 70 m was recorded associating with the sensing displacement. The limitation of this measurement due to the sensing fiber bending radius of 2 mm was noted.

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a Lightwave Technology Research Center, Department of Applied Physics, Faculty of Science King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand.
b National Metrology Institute, Ministry of Science Technology and Environment, Bangkok 10400, Thailand.

* Corresponding author, E-mail: yupapin.preecha@kmitl.ac.th

Received 22 Sep 1999, Accepted 18 Aug 2000